PDP 11 gear finally moved

Tothwolf tothwolf at concentric.net
Tue Jul 21 20:56:36 CDT 2015

On Mon, 20 Jul 2015, Mark J. Blair wrote:
>> On Jul 20, 2015, at 18:02 , Tothwolf <tothwolf at concentric.net> wrote:
>> I replace wax paper types with polyester (mylar), polystyrene or 
>> ceramic discs, depending on how they are used in the circuit (note 
>> however that for wound foil types, modern replacement parts do not mark 
>> the outside foil, which needs to be at ground potential in many tube 
>> circuits, otherwise the circuit can pick up noise and hum).
> Funny that you mentioned that! I just watched a YouTube video today 
> about how to experimentally determine which lead is connected to the 
> outer foil for applications where that's important. Modern film caps may 
> have a stripe on one end, but it doesn't appear to reliably indicate 
> which lead goes to the outer foil.

I've often wondered why they even bother to put that polarity stripe on 
modern film parts when it doesn't actually indicate the outside foil 
terminal. Maybe this is something that has become lost knowledge to 
manufacturers over the years to the point where even Vishay/Sprague 
doesn't know what that black indicator stripe was actually used for?

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